1. Technical Field
The present invention relates generally to a distributed file system and, more particularly, to a technology in which clients participate in fulfilling the function of a data repository in a distributed file system to achieve high-performance access in an environment in which the clients of the file system intensively access a specific data set.
2. Description of the Related Art
Recently, a plurality of Virtual Machines (VMs) is frequently hosted on a single physical server using virtualization technology. By hosting multiple VMs on a single physical server, the utilization of a system can be significantly increased. In addition, the function of VM's live migration can be utilized to balance system-wide workload and overcome difficulties in case of system failures.
For the live migration function of a Virtual Machine (VM), shared storage which is accessible to different server hosts while the hosts share a VM image is indispensible.
Methods of providing shared storage include a Storage Area Network (SAN), Network Attached Storage (NAS), an Internet Small Computer System Interface (iSCSI) storage, and a distributed file system.
The conventional methods of providing shared storage, such as an SAN, NAS and an iSCSI, however, have many problems in terms of storage scalability and easy management. Furthermore, the methods are problematic in that the performance of a client's access to storage may be lowered because access to the storage is concentrated in proportion to the increasing number of clients.
Meanwhile, a distributed file system configured to provide an integrated file system to users and to be sharable among several users by connecting a plurality of computers, each including storage, via a network in various recent Internet environments has recently been being used.
A distributed file system is advantageous in that it provides high scalability by allowing the number of servers participating in the distributed file system to be increased depending on the circumstances, thereby enabling the size of the file system to be easily extended. Furthermore, the distributed file system may provide high availability because it can use a replica of another data storage server when a specific data storage server fails in such a way as to redundantly store replicas of file data in different data storage servers. Furthermore, the distributed file system can improve performance by distributing the read requests of several clients over several storage servers because there are several replicas.
Furthermore, various and improved techniques that use a distributed file system have been introduced, such as a method of moving a VM disk from a piece of physical storage to another piece of physical storage in the state in which a VM is running, which is disclosed in U.S. Patent Application Publication No. 2009/0037680.
This distributed file system is also problematic in that the performance of a client's access to storage is deteriorated in proportion to an increase in the number of clients. The problems in the virtual environment have a fatal limitation that causes the important applications of enterprises, such as database systems, to include a plurality of file systems and then each of the file systems to support only a limited number of clients, or that prevents execution in the virtual environment.